Gravity plate settlers are well known for use in water filtration facilities for separating flocculated solids from an influent flow of liquid. In accordance with well known prior art systems, a plurality of parallel plates are connected in series over a settling tank. An influent flow of liquid is distributed across the width of the plates and then flows upwardly under laminar flow conditions. The solids settle on the plates while the effluent exits from the plates through flow balancing devices at the top. The clarified liquid then flows via effluent troughs along the tops or side of the plates to an outlet gutter. Meanwhile, the solids slide down the plates due to gravitational forces into the settling tank.
In accordance with the known principles of inclined gravity plate liquid clarification, the effective gravity settling area of each plate is equivalent to the actual area of the plate projected on a horizontal surface. Thus, up to 10 square feet of settling area may result from each square foot of land or floor space occupied by the gravity plate settler.
One prominent manufacturer of prior art gravity plate settlers is the Graver Water Division of Ecodyne.
According to such well known prior art parallel plate settlers, the parallel plates are manually and individually mounted between a pair of channel beams which also function as an effluent trough. Individual mounting of the plates is both time consuming and labour intensive. As a result, a number of modular plate settlers have been developed in an effort to overcome these prior art disadvantages.
For example, U.S. Pat. No. 4,515,698 (Stewart) discloses an inclined plate clarifier module which is suspended in position within a clarifying tank by cables or rods attached to a supporting structure such as a bridge. Fastening rings or eyes are secured in a suitable manner to the module to facilitate lifting and lowering and for securing the module in a desired position within the existing liquid clarifying apparatus.
U.S. Pat. No. 3,852,199 (Wachsmuth et al) teaches the use of abutting separate rectangular modules along slanting end surfaces to permit handling and transportation of a modular multi-tube settling device.
The above referenced prior art systems require careful and time consuming installation with expensive equipment, and are difficult to maintain or service. For instance, the system of Wachsmuth et al extends over the full area of the settling tank thereby preventing access to the underside of the plate settler units for cleaning, maintenance or replacement of sludge collecting equipment within the settling tank.
The system of Stewart suffers from the additional disadvantage of being submerged into the settling tank in a manner that renders the through flow of liquid as parallel to the remaining liquid flowing through the clarifier. In other words, the system of Stewart is not integral with the settling tank.
Furthermore, it has been found that the flow of water through the influent flow distribution orifices in prior art systems can be substantially impeded as a result of turbulence generated by the orifices. This can result in reduced overall efficiency of plant performance and the system.
A number of further prior art approaches have attempted to overcome problems relating to uneven liquid flow through the plate settlers. For example, each of U.S. Pat. Nos. 4,120,796 and 4,089,782 (Huebner) and U.S. Pat. No. 3,886,064 (Kosonen) disclose apparatus for providing equal fluid flow via respective ones of the plate channels. These apparatus are self supporting separate unit structures and are specifically associated with series flows through water purification plants.
In particular, U.S. Pat. No. 4,089,782 (Huebner) teaches multiple inlet manifold chambers containing overflow control devices. The overflow control devices have a primary purpose of evenly distributing liquid to be clarified along the length of the respective input manifold chambers so that liquid to be clarified passes uniformly to the inclined flow passages.
In particular, U.S. Pat. No. 4,120,796 (Huebner) teaches flow regulating channel means employed both at the outside lower and outside upper end of each inclined flow passage. With the clarifier operating in an upflow mode, the flow regulating channel means serve to collect clarified effluent and direct it to a central collection reservoir which is in communication with an effluent conduit. The flow regulating channel means arranged at the upper ends of the inclined flow passages are formed from an elongated plate for defining an enclosed region and having a bent lower edge with a lip extending upwardly from the upper surface of the adjacent inclined clarifier plate.
On the other hand, U.S. Pat. No. 3,886,064 (Kosonen) teaches an adjustable regulating plate arranged in a trough in front of the row outlet openings in each side of a lamellar separator. Spaced apart elongated attachment apertures are arranged vertically in the regulating plates at each end so that the regulating plates can be adjusted to fit the sides of the separator by means of attachment bolts. The regulating plates are usually arranged so that the attachment bolts pass through the upper part of the attachment apertures.
None of the prior art patents teach interchangeability, efficiency and inexpensive means for balancing the flow of liquid to each plate under all flow conditions. Instead, the above prior art systems provide fixed, complex and expensive manufactured features for accomplishing this aim. Moreover, such prior art systems render periodic flushing, cleaning and servicing of the plate settlers both time consuming and labour intensive.